A developer including a colored resin particle and an external additive added to a surface of the colored resin particle and having a diameter smaller than or equal to 200 nm is provided. The external additive includes a nitrogen-containing resin particle. In elemental analysis of the nitrogen-containing resin particle, a peak appearing in a range of 0.38-0.42 keV is expressed as an N-peak, and a peak appearing in a range of 0.48-0.52 keV is expressed as an O-peak. Maximum count numbers in the N-peak and the O-peak of the external additive on a surface of the colored resin particle are respectively expressed as N1 and O1. Maximum count numbers in the N-peak and the O-peak of the surface of the colored resin particle where no external additive is observed are respectively expressed as N2 and O2. The count numbers N1, O1, N2 and O2 satisfy 1.7(N2/O2)<(N1/O1).

Herein is disclosed a method for electrostatic printing. The method may comprise: a. electrostatically printing a discontinuous layer of a transparent electrostatic ink in a first area on a print substrate; b. electrostatically printing an image comprising a coloured electrostatic ink on the print substrate in a second area, which may or may not be in the same location as the first area, wherein the electrostatic printing in each of steps a and b involves, respectively, transferring the transparent electrostatic ink or the coloured electrostatic ink from a photoimaging plate to the print substrate via an intermediate transfer member. The method may then involve repeating steps a and b on the same or different print substrates, wherein each repeat of step b results in the same or a different printed image, and the discontinuous layer of transparent electrostatic ink varies between at least two different printing patterns. A system is also disclosed herein.

Toner particles each contain a binder resin and a releasing agent. The releasing agent includes an ester mixture. The ester mixture includes an ester and a fatty acid. The ester includes at least one monoester. The monoester is a dehydration condensation product of a monovalent linear saturated carboxylic acid and a monovalent linear saturated alcohol. The fatty acid includes at least one monovalent linear saturated carboxylic acid. The fatty acid includes a monovalent linear saturated carboxylic acid having a carbon number of at least 14 and no greater than 24 but does not include a monovalent linear saturated carboxylic acid having a carbon number of less than 14 or a monovalent linear saturated carboxylic acid having a carbon number of greater than 24. The fatty acid has a melting point of 60 C. to 80 C. The fatty acid accounts for 5% by mass to 20% by mass of the ester mixture.

Provided is a toner including a binder resin, wherein the toner includes a THF-insoluble component in an amount of from 10% by mass through 40% by mass, a molecular weight distribution of a THF-soluble component of the toner measured by gel permeation chromatography (GPC) has a main peak between 10,000 and 16,000, and a half value width of the main peak is a molecular weight of from 60,000 through 90,000, and the THF-soluble component of the toner includes a component having a molecular weight of 2,000 or less in an amount of from 15.0% by mass through 25.0% by mass, and a component having a molecular weight of 100,000 or greater in an amount of 10.0% by mass or less as measured by GPC.

There is provided a toner set including a yellow toner, a cyan toner and a magenta toner, the toners each comprising an external additive and colored resin particles comprising a binder resin, a colorant and a charge control agent. An absolute value of an average of q/d for any of the yellow, cyan and magenta toners is expressed by charge amount q (fC) and particle diameter d (m). It is obtained by measurement using an electric field detachment-type charge amount distribution measurement device. It is in a range of 2.0 to 6.5 fC/10 m, and a standard deviation (SD) of q/d is 13 fC/10 m or less. A difference between average values of q/d for any two of the yellow, cyan and magenta toners is 2.0 fC/10 m or less. A difference (SD) between standard deviations of q/d for the two toners is 5.0 fC/10 m or less.

There is provided a toner set including a yellow toner, a cyan toner and a magenta toner, the toners each comprising an external additive and colored resin particles comprising a binder resin, a colorant and a charge control agent. An absolute value of an average of q/d for any of the yellow, cyan and magenta toners is expressed by charge amount q (fC) and particle diameter d (m). It is obtained by measurement using an electric field detachment-type charge amount distribution measurement device. It is in a range of 2.0 to 6.5 fC/10 m, and a standard deviation (SD) of q/d is 13 fC/10 m or less. A difference between average values of q/d for any two of the yellow, cyan and magenta toners is 2.0 fC/10 m or less. A difference (SD) between standard deviations of q/d for the two toners is 5.0 fC/10 m or less.

A toner has positive chargeability. Particles of the toner each include a toner mother particle and external additive particles adhering to a surface of the toner mother particle. The external additive particles include first external additive particles and second external additive particles. The first external additive particles have positive chargeability and are each a first silica particle having a surface treated with a positive chargeability imparting agent and a hydrophobing agent. The second external additive particles have negative chargeability and are each a second silica particle having a surface treated only with a silane compound. The silane compound is at least one alkylalkoxysilane represented by formula (I) shown below. In formula (I), R.sup.1 represents an alkyl group having a carbon number of at least 8 and no greater than 16. R.sup.2, R.sup.3, and R.sup.4 each represent, independently of one another, an optionally substituted hydrocarbon group. ##STR00001##

Toner particles each include a toner mother particle and a plurality of C/S external additive particles. The toner mother particle contains a polyester resin. The C/S external additive particles each adhere to a surface of the toner mother particle and include a core particle and a plurality of shell particles. The shell particles each adhere to a surface of the core particle. The shell particles have a number average primary particle diameter of no greater than 0.40 times a number average primary particle diameter of the core particles. The core particles and the shell particles each contain a resin. The core particles have a hydrophobicity degree of at least 30%. The shell particles have a hydrophobicity degree of no greater than 5%. The C/S external additive particles have a hydrophobicity degree of at least 15% and no greater than 25%.

A toner for developing electrostatic images, including toner particles containing an external additive on surfaces of toner matrix particles. The external additive contains at least a lanthanum-containing titanate compound.

Provided is a toner including toner base particles and an external additive, wherein each of the toner base particles includes a binder resin, a release agent, and silica, an average abundance ratio (X.sub.surf) of the silica on a region adjacent to a surface of the toner base particle is from 70% through 90%, and a projected area average value S(180) per particle of the toner when the toner is heated to 180 C. and a projected area average value S(30) per particle of the toner when the toner is 30 C. satisfy Formula (1) below,

1.4S(180)/S(30)1.7Formula (1).